Dinosaurs? & Dinosaur Wars � Frederick P. Brooks' Mythical Man-Month (1975). Description of the software crises - likens large scale programming to a tarpit � CSCI 6730 / 4730 No scene from prehistory is quite so vivid as that of the mortal struggles of Operating Systems great beasts in the tar pits. In the mind's eye one sees dinosaurs , mammoths, and saber toothed tigers struggling against the grip of the tar . The fiercer the struggle, the more entangling the tar , and no beast is so strong or so skillful but that he ultimately sinks. Operating Systems Overview Large-scale programming has over the past decade been such a tar pit , and many great and powerful beasts have thrashed violently in it. Most have emerged with running systems - few have met goals, schedules, and budgets. 2 Maria Hybinette, UGA Maria Hybinette, UGA Evolution of our Textbook Outline & Questions � � What is an Operating Systems (OS)? � � What does an OS do? � � What is an OS and what is it not? � � How do I run an OS? � � How does an Operating System run? 1983 1998 2004 � � What is the basic structure? � � Computer System Component Architecture 3 4 2008 Maria Hybinette, UGA Maria Hybinette, UGA C.R.Knight, Mural of La Brea Tar Pits. Los Angeles County Natural History Museum. �� Questions? Poll? � � What are the major operating system � � What desktop/laptop OS do you have? components? � � Which desktop/laptop OSs are you familiar � � What are basic computer system with? organizations? � � What do you think the market share (%) is (portion of different ODs)? � � How do you communicate with the operating systems? � � What services are (need to be) provided? 5 6 Maria Hybinette, UGA Maria Hybinette, UGA
Popularity: The Desktop OS Market Share What is an Operating System? � � A hardware manager � � A program that acts as an intermediary between a user of a computer and the computer hardware. » � Execute user programs and make solving user problems easier. � � Operating system goals: » � Make the computer system convenient to use. » � Use the computer hardware in an efficient manner. » � Combination of the above. » � Handhelds (convenience), Mainframes/Servers 7 8 (efficiency) http://en.wikipedia.org/wiki/Image:Os_as_of_2008.png Maria Hybinette, UGA Maria Hybinette, UGA Where is the OS? Computer System Layers Computer System Layers Computer system can be divided Computer system can be divided roughly in four components: roughly in four components: � … … � � � Hardware user � user � user � � � Hardware: user � user � user � 1 � 2 � n � 1 � 2 � � n � � Operating system » � provides basic computer resources: � � Application programs … … – � CPU, Memory, I/O Devices compiler assembler text editor compiler assembler text editor � � Users System and Application Programs System and Application Programs Operating System Operating System Computer Computer Hardware Hardware 9 10 Maria Hybinette, UGA Maria Hybinette, UGA Computer System Layers Computer System Layers Computer system can be divided Computer system can be divided roughly in four components: roughly in four components: … � � … � � Hardware user � user � user � � � Hardware user � user � user � 1 � 2 � n � 1 � 2 � n � � � Operating system: � � Operating system » � Controls and coordinates � � Application programs … … use of hardware among compiler assembler text editor compiler assembler text editor various applications and » � define the ways in which the System and Application Programs System and Application Programs users. system resources are used to solve the computing Operating System Operating System problems of the users – � Word processors, Computer Computer compilers, web browsers, Hardware database systems, video Hardware games 11 12 Maria Hybinette, UGA Maria Hybinette, UGA
Computer System Layers Computer System Layers Computer system can be divided Computer system can be divided roughly in four components: roughly in four components: … � … � � � Hardware user � user � user � � � Hardware user � user � user � 1 � 2 � n � 1 � 2 � � n � � Operating system � � Operating system � � Application programs � � Application programs … … compiler assembler text editor compiler assembler text editor � � Users � � Users System and Application Programs System and Application Programs » � People, machines, other computers Operating System Operating System Computer Computer Hardware Hardware 13 14 Maria Hybinette, UGA Maria Hybinette, UGA What Does Operating Systems Do? What “ Makes up” the Operating System? � � No universally accepted definition! � � A Space/Time Controller � � It allocates resources � � “Everything a vendor ships when you order an operating system” used to be a good » � Manages all resources approximation… But varies wildly » � Decides between conflicting requests for efficient and fair resource use � � Operating System is the “Kernel” � � It controls execution » � the one program that runs at all times on the computer » � Controls execution of programs to prevent errors » � everything else is either a and improper use of the computer – � system program (ships with the operating system) or an – � application program 15 16 Maria Hybinette, UGA Maria Hybinette, UGA Visual of the Time-Line of the The Computer Startup Process Booting Sequence � � A bootstrap program (initial program) is loaded at power- up or reboot » � Stored in firmware in ROM/ EEROM » � Stored on a chip on the motherboard (‘parentboard’) � � Initializes all aspects of system � � Loads operating system kernel (e.g., from disk) and Added Slide to aid in visualizing the booting sequence - please starts execution read the below web page for more detail (HW). � � Pentium initial boot strap program is called the system Basic Input Output System or http://duartes.org/gustavo/blog/post/how-computers-boot-up BIOS. 17 18 Maria Hybinette, UGA Maria Hybinette, UGA
CMOS/BIOS Configuration Utility Booting from hard disk Disk is divided into 1+ partitions: one file system per partition � Partition Table Entire Disk: MBR Partition Partition … Partition Free Space Management File System: Boot block Super Block i-list Data blocks for files, directories, etc. i-node i-node i-node … i-node 19 20 Maria Hybinette, UGA Maria Hybinette, UGA Entire Disk & Booting Computer Partition Layout � � Boot block: � � Master Boot Record (sector 0) - Pentium » � contains a hardware specific program that is called automatically to load “UNIX” at system startup time » � used to boot computer � � Super block: � � Partition Table » � file system type, #blocks in file system » � staring and ending address of each partition � � Free space management (two lists): � � “A program (e.g., the system Basic Input Output » � a chain of free data block numbers System or BIOS for Pentiums)” reads in and executes » � a chain of free i-node numbers the MBR � � i-list/i-node table: » � searches for first active partition (noted in the partition » � administrative information about a file (meta-data: name, type, table) location, size, protection bits, … ) structured into an array: inode table or simply the i-list » � reads in its first block (the boot block) and executes it. » � An i-node number: – � uniquely identifies a file in a file system – � is an index to the i-node table Partition Table Boot block Super Block i-list Data blocks for files, directories, etc. MBR Partition Partition … Partition 21 22 Free Space Management Maria Hybinette, UGA Maria Hybinette, UGA Computer System Organization Computer System Operations � � CPU: the processor that perform the actual computation � � I/O controll/ers: » � take commands in registers, generate flags and interrupts » � each device controller – � is in charge of a particular device type – � has a local buffer for I/O – � Examples: audio – output device, mouse – input, disk – I/O. � � CPU moves data from/to main memory to/from local buffers. � � I/O is from the device to local buffer of controller. � � One or more CPUs, device controllers connect through � � Device controller informs CPU that it has finished its common bus providing access to shared memory operation by causing an interrupt . � � Concurrent execution of CPUs and devices competing for memory cycles 23 24 Maria Hybinette, UGA Maria Hybinette, UGA
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